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Transport in Plants. Section 3.4 Unit C. Objectives. distinguish between cohesion and adhesion, giving examples describe water transport from root to leaf including different processes used relate tonicity of plant environment to movement of water in and out of the cell - PowerPoint PPT Presentation
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SECTION 3 .4UNIT C
Transport in Plants
Objectives
distinguish between cohesion and adhesion, giving examples
describe water transport from root to leaf including different processes used
relate tonicity of plant environment to movement of water in and out of the cell
summarize the process of sugar transport in plants
Review
What is osmosis?What is diffusion?What is active transport?What is transpiration? Where does it take
place?
Plant Transport of Water: 3 Main Steps
1) Water uptake in roots – root pressure2) Cohesion & Adhesion in Xylem 3) Leaf transpiration
Animation:
http://www.biology.ualberta.ca/facilities/multimedia/uploads/alberta/transport.html
Root Pressure
Movement of water from roots to leavesPressure built up in xylemDissolved minerals in root cells due to active
transportWater enters cell, creating positive pressure,
forcing fluid up the xylemWater forced from area of higher pressure in
roots to area of lower pressure in leaves
Root Pressure
When would root pressure not be the complete explanation for water movement in plants? When the plant is very large (maximum of a few
metres)Overall process affected by transpiration
Cohesion and Adhesion
Cohesion Attraction of water molecules to other water
molecules Due to polar nature of water (slightly positive end
attracts slightly negative end of another water molecule)
Cohesion and Adhesion
Adhesion Attraction of water molecules to molecules of other
substances Usually polar interactions
Cohesion & Adhesion in the plant
Cohesion and adhesion are two properties of water that helps it to travel from roots to leaves.
Cohesion Causes water molecules to cling to each other
Adhesion allows water to pull itself up the plant
Video: http://www.youtube.com/watch?v=EKyHbanzYnI&feature=related
Trees & Capillary Action: http://www.davidlnelson.md/Cazadero/Trees&CapillaryAction.htm
Transpiration
Evaporation of water through stomata and lenticels through transpiration creates a tension or transpiration pull.
When combined with cohesion, adhesion, and root pressure, water is able to be drawn up the xylem.
Transpiration is dependent on temperature. Higher temperatures increase the rate of evaporation and cause rapid movement in xylem.
Video: Plant Transport - Summary
http://www.youtube.com/watch?v=U4rzLhz4HHk&feature=related
Why would the carnation/celery change color?
How is it related to root pressure and transpiration? Transpiration causes the loss of water through the
stem and leaves. This water must be replaced, drawing water up from
the roots Note that only certain cells in the celery are stained
Which cells might these be? Xylem
Do Now
Individually, write a story of water transport in a large plant using the information on p. 317-318. You are writing it from the point of view of the water molecule.
Explain in your story how the plant uses adhesion and cohesion properties of water to its advantage
Include the different transport mechanisms used at different parts of the plant Root Pressure, Adhesion, Cohesion, Transpiration
Tonicity & its Effect on the Plant
Tonicity concentration of solute particles in an solution Related to hypertonic and hypotonic (which one would
have a higher tonicity?)What will happen to a plant cell that is placed
in a concentrated salt solution? Water leaves the plant cell by osmosis Effect = plasmolysis (cell looks shrunken) Water leaves vacuole, cell contents pull into center, cell membrane becomes visible
Hypertonic solution
Hypotonic solution
Question
What would happen to a plant that was placed in a hypertonic solution (salt solution)? Becomes flaccid
What would happen to the plant when it was moved from this solution to a hypotonic environment? Becomes turgid
Sugar Transport
Phloem is essential Removal causes plant death
Takes sugar from source (leaves) to place to be used/stored (sink)
Composed of sieve tube cells Need companion cells to control its activity Why? Uses carrier proteins and active transport to take in
sugar molecules
Sugar Transport
If sugar is being moved into the cells, what else will follow it? Water!
Increased pressure pushes water and sugars through phloem to rest of plant
Called the pressure-flow theory
Sugar Uses
Actively transported from sieve cells in phloem to adjacent cells
Use: Growth Respiration Other life processes
Stored in roots, stems, or leavesWater follows movement of sugar and can:
Increase turgidity of other cells Leave through transpiration Move into xylem
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